如何爲泛型類指定泛型集合類型？

Question

說我正在創建一個泛型類，我也想使通用成員以通用方式存儲的集合。這樣做的正確語法是什麼？在試圖越過我想要做的就是，通過最好的猜測是如下：

class AdjacencyList<VertexType, EdgeType, VertexCollectionType: Collection, EdgeCollectionType: Collection> { 
    var vertices: VertexCollectionType<Vertex<VertexType>> 
    var edges: EdgeCollectionType<Edge<EdgeType>> 

    init() { 
     self.vertices = VertexCollectionType<VertexType>() 
     self.edges = EdgeCollectionType<EdgeType>() 
    } 
} 

class Vertex<VertexType> { ... } 
class Edge<EdgeType> { ... } 

Answer 1

根據您是否使用自定義集合類型，還是你想創造AdjacencyList新實例時指定它們，你可以逃脫類似於：

class Vertex<VertexType> { } 

class Edge<EdgeType> { } 

class AdjacencyList<VertexType, EdgeType> { 
    var vertices: [Vertex<VertexType>] = [] 
    var edges: [Edge<EdgeType>] = [] 
} 

let list = AdjacencyList<String, Int>() 
list.vertices // [Vertex<String>] 
list.edges // [Edge<Int>] 

或者，如果你希望能夠指定每一次，你可以做一些類似這樣（的代碼是在雨燕3一些集合類型，所以VC.Iterator.Element應VC.Generator.Element和Collection變成CollectionType如果您使用Swift 2）

class AdjacencyList <V, E, VC: Collection, EC: Collection 
    where VC.Iterator.Element == Vertex<V>, EC.Iterator.Element == Edge<E>> { 

    var vertices: VC 
    var edges: EC 

    init(vertices: VC, edges: EC) { 
     self.vertices = vertices 
     self.edges = edges 
    } 
} 

let arrayList = AdjacencyList<String, Int, Array<Vertex<String>>, Array<Edge<Int>>>(vertices: [], edges: []) 
arrayList.vertices // [Vertex<String>] 
arrayList.edges // [Edge<Int>] 

// as long as Vertex and Edge are Hashable 
let setList = AdjacencyList<String, Int, Set<Vertex<String>>, Set<Edge<Int>>>(vertices: [], edges: []) 
setList.vertices // Set<Vertex<String>> 
setList.edges // Set<Edge<Int>>